POSITIVE ELECTRODE MATERIALS WITH HIGH OPERATING VOLTAGE FOR LITHIUM BATTERIES - LICRYMN2-YO4 (0-LESS-THAN-OR-EQUAL-TO-Y-LESS-THAN-OR-EQUAL-TO-1)

Reversible lithium deintercalation of chromium-substituted spinel manganese oxides LiCryMn2-yO4(0 less than or equal to y less than or equal to 1) in the voltage range 3.4-5.4 V versus Li, occurs in two main steps for 0<y<1: one at about 4.9 V and the other at about 4 V. The 4.9 V process capacity increases with the chromium content while the 4 V process capacity decreases at the same time. Excellent cyclability was observed for y less than or equal to 0.5 while materials with y greater than or equal to 0.75 were loosing capacity rapidly upon cycling. Changing the chromium composition of these materials enables the control of the average intercalation voltage in the range 4.05-4.5 V versus Li, a voltage range where no material was known before. A low manganese to chromium substitution rate in LiMn2O4 was found to be beneficial to the specific capacity and energy and to the cyclability of the spinel materials. Due to the selected electrolyte composition with high stability against oxidation, extra capacity due to electrolyte oxidation at each cycle remained very low even though the charge voltage was highly oxidative.